Light emitting diodes (LEDs), as a low-power consumption, environmentally friendly light source, are widely applied in the fields such as lighting and backlight display. To make an LED emit stable light, a current flowing through the LED is required to be relatively constant, and especially, when LEDs are used as a backlight source for a display, the currents flowing through each LED chip are further required be equalized as much as possible, in order to achieve a desirable display effect. In other words, a constant current control circuit is an indispensable module of an LED light source.
Nowadays, commercially available constant current control circuits generally require using power transistors including NMOS, PMOS, NPN and PNP power transistors to regulate the voltage drop related to each power transistor, so as to implement current regulation to make the currents flowing through different LED chips equal. If the power transistors are built-in, the chip area is increased, and the chip cost is also increased. Also, the heat dissipation problem of the power transistors cannot be solved easily.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.